Mean arterial pressure, O2-uptake, and muscle force time during dynamic and rhythmic-static exercise in men with high percentages of fast- and slow-twitch fibers

The influence of different percentages of slow-twitch (ST) and fast-twitch (FT) fibers in vastus lateralis on the relationship between mean arterial pressure (MAP) and O₂-uptake ( \(\dot V\) O₂) with muscle force time (MIpm, ⁶⁰∫₀ p×t) exerted on the pedal during upright cycling, or during rhythmic isometric contraction (RIC) (only one subject) was studied in three high percent ST men (average 78% ST) (ST group), and in three high percent FT men (average 75% FT) FT group). MAP, or MIpm, was higher and had a steeper linear regression in the FT group than in the ST group at or against the same absolute \(\dot V\) O₂ during cycling at 60 rpm, or 100 rpm. The relationship between MAP and MIpm, however, was almost the same between both in the FT and ST group, or between both at 60 and 100 rpm. During RIC the slope (δy/δx) of the linear regression line between MAP and MIpm was close to that during cycling, whereas the slope of \(\dot V\) O₂ vs. MIpm was much lower. In conclusion, the variations in fiber population in working muscle do not seem to have any effect on MAP. MAP increases with MIpm independent of fiber population and/or fitness ( \(\dot V\) O₂ max).